Logo Search packages:      
Sourcecode: qt4-x11 version File versions  Download package

QPaintDevice Class Reference

Inheritance diagram for QPaintDevice:

QGLFramebufferObject QGLPixelBuffer QImage QPicture QPixmap QPrinter QSvgGenerator QWidget

List of all members.

Detailed Description

The QPaintDevice class is the base class of objects that can be painted.

A paint device is an abstraction of a two-dimensional space that can be drawn using a QPainter. Its default coordinate system has its origin located at the top-left position. X increases to the right and Y increases downwards. The unit is one pixel.

The drawing capabilities of QPaintDevice are currently implemented by the QWidget, QImage, QPixmap, QGLPixelBuffer, QPicture, and QPrinter subclasses.

To implement support for a new backend, you must derive from QPaintDevice and reimplement the virtual paintEngine() function to tell QPainter which paint engine should be used to draw on this particular device. Note that you also must create a corresponding paint engine to be able to draw on the device, i.e derive from QPaintEngine and reimplement its virtual functions.

Qt requires that a QApplication object exists before any paint devices can be created. Paint devices access window system resources, and these resources are not initialized before an application object is created.
The QPaintDevice class provides several functions returning the various device metrics: The depth() function returns its bit depth (number of bit planes). The height() function returns its height in default coordinate system units (e.g. pixels for QPixmap and QWidget) while heightMM() returns the height of the device in millimeters. Similiarily, the width() and widthMM() functions return the width of the device in default coordinate system units and in millimeters, respectively. Alternatively, the protected metric() function can be used to retrieve the metric information by specifying the desired PaintDeviceMetric as argument.

The logicalDpiX() and logicalDpiY() functions return the horizontal and vertical resolution of the device in dots per inch. The physicalDpiX() and physicalDpiY() functions also return the resolution of the device in dots per inch, but note that if the logical and vertical resolution differ, the corresponding QPaintEngine must handle the mapping. Finally, the numColors() function returns the number of different colors available for the paint device.

See also:
QPaintEngine, QPainter, {The Coordinate System}, {The Paint System}

Definition at line 60 of file qpaintdevice.h.

Public Types

enum  PaintDeviceMetric {
  PdmWidth = 1, PdmHeight, PdmWidthMM, PdmHeightMM,
  PdmNumColors, PdmDepth, PdmDpiX, PdmDpiY,
  PdmPhysicalDpiX, PdmPhysicalDpiY

Public Member Functions

int depth () const
virtual int devType () const
int height () const
int heightMM () const
int logicalDpiX () const
int logicalDpiY () const
int numColors () const
virtual QPaintEnginepaintEngine () const =0
bool paintingActive () const
int physicalDpiX () const
int physicalDpiY () const
int width () const
int widthMM () const
virtual ~QPaintDevice ()

Protected Member Functions

virtual int metric (PaintDeviceMetric metric) const
 QPaintDevice ()

Protected Attributes

ushort painters


class QFontEngineMac
class QPainter
class QX11PaintEngine

Related Functions

(Note that these are not member functions.)

const Q_GUI_EXPORT QX11Infoqt_x11Info (const QPaintDevice *pd)

The documentation for this class was generated from the following files:

Generated by  Doxygen 1.6.0   Back to index